US20100048016A1 - Semiconductor device manufacturing method - Google Patents

Semiconductor device manufacturing method Download PDF

Info

Publication number
US20100048016A1
US20100048016A1 US12/461,577 US46157709A US2010048016A1 US 20100048016 A1 US20100048016 A1 US 20100048016A1 US 46157709 A US46157709 A US 46157709A US 2010048016 A1 US2010048016 A1 US 2010048016A1
Authority
US
United States
Prior art keywords
layer
etching
algaas
gaas
inalgaas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
US12/461,577
Other versions
US7981787B2 (en
Inventor
Takayuki Izumi
Ryoji Shigemasa
Tomoyuki Ohshima
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Neophotonics Corp
Original Assignee
Oki Semiconductor Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Oki Semiconductor Co Ltd filed Critical Oki Semiconductor Co Ltd
Assigned to OKI SEMICONDUCTOR CO., LTD. reassignment OKI SEMICONDUCTOR CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: IZUMI, TAKAYUKI, OHSHIMA, TOMOYUKI, SHIGEMASA, RYOJI
Publication of US20100048016A1 publication Critical patent/US20100048016A1/en
Application granted granted Critical
Publication of US7981787B2 publication Critical patent/US7981787B2/en
Assigned to NEOPHOTONICS SEMICONDUCTOR GK reassignment NEOPHOTONICS SEMICONDUCTOR GK ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: Lapis Semiconductor Co., Ltd.
Assigned to Lapis Semiconductor Co., Ltd. reassignment Lapis Semiconductor Co., Ltd. CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). Assignors: OKI SEMICONDUCTOR CO., LTD.
Assigned to NEOPHOTONICS CORPORATION reassignment NEOPHOTONICS CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: NEOPHOTONICS SEMICONDUCTOR GK
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/30604—Chemical etching
    • H01L21/30612—Etching of AIIIBV compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
    • H01L29/08—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions with semiconductor regions connected to an electrode carrying current to be rectified, amplified or switched and such electrode being part of a semiconductor device which comprises three or more electrodes
    • H01L29/0843—Source or drain regions of field-effect devices
    • H01L29/0891—Source or drain regions of field-effect devices of field-effect transistors with Schottky gate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/66007—Multistep manufacturing processes
    • H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
    • H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
    • H01L29/66409—Unipolar field-effect transistors
    • H01L29/66446—Unipolar field-effect transistors with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET]
    • H01L29/66462—Unipolar field-effect transistors with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET] with a heterojunction interface channel or gate, e.g. HFET, HIGFET, SISFET, HJFET, HEMT
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/66007—Multistep manufacturing processes
    • H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
    • H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
    • H01L29/66409—Unipolar field-effect transistors
    • H01L29/66848—Unipolar field-effect transistors with a Schottky gate, i.e. MESFET
    • H01L29/66856—Unipolar field-effect transistors with a Schottky gate, i.e. MESFET with an active layer made of a group 13/15 material
    • H01L29/66863—Lateral single gate transistors
    • H01L29/66871—Processes wherein the final gate is made after the formation of the source and drain regions in the active layer, e.g. dummy-gate processes

Definitions

  • the present invention relates to a manufacturing method for a semiconductor device, and more particularly, to a manufacturing method for a semiconductor device in order to acquire a HEMT (High electron mobility transistor) or a MESFET (Metal-Semiconductor Field Effect Transistor), for example.
  • HEMT High electron mobility transistor
  • MESFET Metal-Semiconductor Field Effect Transistor
  • JP-A Japanese Patent Application Laid-Open
  • one semiconductor device may have a double recess structure having a small through hole called inner recess within a through hole called wide recess, and having a gate electrode imbedded in the small through hole and also disposed on the edge part thereof (refer to “Low Voltage Operation Power Heterojunction FET with Low on-resistance for Personal Digital Cellular Phones”, TECHNICAL REPORT OF IEICE (The Institute of Electronics, Information and Communication Engineers) ED98-215, MW98-178, ICD98-282 (1999-01), for example).
  • the semiconductor device has an etching stopper layer for performing selective etching.
  • an AlGaAs layer having a higher mixing ratio of Al (approximately 20% or higher) or an AlAs layer is used as an etching stopper layer.
  • the AlGaAs layer with the higher mixing ratio of Al or AlAs layer as an etching stopper layer has a larger band gap than that of a GaAs layer or an InGaAs layer, conduction band discontinuity increases.
  • the conduction band discontinuity becomes a barrier against electrons, which increases the contact resistance, for example, and results in a device with a larger parasitic resistance.
  • a semiconductor device manufacturing method comprising:
  • a ratio of In:Al of the InAlGaAs layer is in a range of approximately 4:6 to approximately 6:4 and a ratio of (In+Al):Ga of the InAlGaAs layer is in a range of approximately 1.5:8.5 to approximately 5:5.
  • a semiconductor device manufacturing method comprising:
  • a laminated member in which at least an AlGaAs electron donating layer or an AlGaAs Schottky layer, a GaAs gate-buried layer, an InAlGaAs etching stopper layer, and a GaAs contact layer are laminated on or above a substrate in this order;
  • a ratio of In:Al of the InAlGaAs etching stopper layer is in a range of approximately 4:6 to approximately 6:4 and a ratio of (In+Al):Ga of the InAlGaAs etching stopper layer is in a range of approximately 1.5:8.5 to approximately 5:5.
  • a semiconductor device manufacturing method comprising:
  • a semiconductor device manufacturing method comprising:
  • a ratio of In:Al of the InAlGaAs etching stopper layer is in a range of approximately 4:6 to approximately 6:4.
  • FIG. 1 is a schematic cross-sectional view for explaining a manufacturing process for a semiconductor device according to a first embodiment
  • FIGS. 2A to 2E are process charts for explaining the manufacturing process for the semiconductor device according to the first embodiment
  • FIG. 3 is a schematic diagram showing a conduction band of an HEMT acquired by the manufacturing method for the semiconductor device according to the first embodiment
  • FIG. 4 is a diagram showing changes in etching rate according to the composition ratios of an In AlGaAs layer and an AlGaAs layer;
  • FIG. 5 is a schematic cross-sectional view for explaining a manufacturing process for a semiconductor device according to a second embodiment
  • FIGS. 6A to 6E are process charts for explaining the manufacturing process for the semiconductor device according to the second embodiment.
  • FIG. 7 is a schematic diagram showing a conduction band of an HEMT acquired by the manufacturing method for a semiconductor device according to the second embodiment.
  • FIGS. 1 and 2 a manufacturing method for a semiconductor device according to a first embodiment will be explained.
  • the manufacturing method for the semiconductor device according to the first embodiment is a method for manufacturing an AlGaAs/InGaAs HEMT with a double recess structure, for example.
  • vapor deposition is used to form epitaxial layers on a GaAs substrate 128 .
  • the epitaxial layers are formed by epitaxial growth to include, from the uppermost layer side, an n-GaAs contact layer 110 (500 ⁇ thick, which is a second GaAs layer), an In 0.2 Al 0.2 Ga 0.6 As etching stopper layer 112 (100 ⁇ thick, which will be called InAlGaAs etching stopper layer 112 below), an undoped-GaAs gate buried layer 114 (200 ⁇ thick, which is a first GaAs layer), an n-AlGaAs electron donating layer 116 (250 ⁇ thick), an undoped-Al 0.25 Ga 0.75 As spacer layer 118 (30 ⁇ thick), an In 0.2 Ga 0.8 As channel layer 120 (100 ⁇ thick), an undoped-Al 0.25 Ga 0.75 As spacer layer 122 (50 ⁇ thick), an n-As contact layer 110 (500 ⁇ thick, which is
  • vacuum evaporation and/or the sputtering method is used to form two ohmic electrodes on the n-GaAs contact layer 110 , which are used as a source electrode 130 A and a drain electrode 130 B.
  • photolithography is used to provide a photoresist (not shown) having an opening pattern on the n-GaAs contact layer 110 .
  • selective etching using a mixed solution (etchant) of tri-ammonium citrate, oxygenated water and water is performed on the n-GaAs contact layer 110 between the source electrode 130 A and the drain electrode 130 B to form a wide recess 132 (which is a first through hole).
  • the mixing ratio of the mixed solution (etchant) is, for example, tri-ammonium citrate salt/25 g:oxygenated water/40 cc:water/2000 cc.
  • the InAlGaAs etching stopper layer 112 is little etched because the etching rate of the n-GaAs contact layer 110 is about 1000 ⁇ /min while the etching rate of the InAlGaAs etching stopper layer 112 is 10 ⁇ /min or lower, for example. Therefore, the InAlGaAs etching stopper layer 112 stops the etching.
  • a mixed solution (which is an etchant a nonselective etchant) of phosphoric acid, oxygenated water and water, for example, is used to perform nonselective etching (uniform etching) on the InAlGaAs etching stopper layer 112 , whereby making a wide recess 132 reach the undoped-GaAs gate buried layer 114 .
  • the mixing ratio of the mixed solution (etchant) is phosphoric acid/100 cc:oxygenated water/5 cc:water/2100 cc.
  • the depth of the wide recess 132 as a result of the etching on the InAlGaAs etching stopper layer 112 corresponds to a second through hole.
  • the etching is not required to reach the undoped-GaAs gate buried layer 114 , but the etching may be stopped on the way. Then, after a photoresist (not shown) for forming an inner recess 134 , which will be described later, is provided, the InAlGaAs etching stopper layer 112 remaining on the undoped-GaAs gate buried layer 114 may be removed by etching.
  • photolithography is used to provide a photoresist (not shown) having an opening pattern both on the n-GaAs contact layer 110 and on the undoped-GaAs gate buried layer 114 exposed by the wide recess 132 .
  • the inner recess 134 (which is a third through hole), which is smaller than the wide recess 132 , is formed within the wide recess 132 .
  • the selective etching stops at the n-AlGaAs electron donating layer 116 .
  • a gate electrode 136 which is imbedded in the inner recess 134 and is also formed on the edge part of the inner recess 134 of the undoped-GaAs gate buried layer 114 (that is, on the undoped-GaAs gate buried layer 114 around the opening part of the inner recess 134 ).
  • the InAlGaAs layer (which is the InAlGaAs etching stopper layer 112 ) is provided between the two GaAs layers (which is the n-GaAs contact layer 110 and the undoped-GaAs gate buried layer 114 ).
  • the In 0.2 Al 0.2 Ga 0.6 As layer is used as the InAlGaAs layer functioning as an etching stopper layer.
  • a ratio of In:Al of the InAlGaAs etching stopper layer is preferably in a range of 4:6 to 6:4, and a ratio of (In+Al):Ga of the InAlGaAs etching stopper layer is preferably in a range of 1.5:8.5 to 5:5.
  • the InAlGaAs layer functioning as the etching stopper layer has a sufficiently low etching rate with respect to the n-GaAs contact layer 110 (which is the second GaAs layer), the InAlGaAs layer can fully exhibit the function as an etching stopper layer.
  • the InAlGaAs layer as an etching stopper layer has a sufficiently low barrier against the GaAs layers (which are the n-GaAs contact layer 110 and the undoped-GaAs gate buried layer 114 ) in the conduction of electrons, which can suppress the increase in contact resistance.
  • an InAlGaAs layer containing In can have a sufficiently low barrier against an GaAs layer.
  • a threshold thickness at which dislocation does not occur exists and depends on a degree of mismatching with the lattice constant of a base. Therefore, the composition and thickness may not be selected freely.
  • the threshold thickness in this case is about 130 ⁇ .
  • the contact resistance decreases with respect to the GaAs layer.
  • the threshold thickness decreases, the thickness providing the sufficient function as an etching stopper layer may not be obtained. Therefore, in this embodiment, the InAlGaAs layer having the above-mentioned predetermined composition ratio allows lattice matching and can be formed in thickness allowing the sufficient function as an etching stopper layer (more specifically, such as 100 ⁇ or thicker), and the contact resistance can be reduced.
  • the InAlGaAs layer having the above-mentioned predetermined composition can be used as an etching stopper layer to perform selective etching with high precision between two GaAs layers and can suppress the increase in contact resistance.
  • the etching depth can be controlled with high precision, and a device with a low parasitic resistance (more specifically, such as a device with a low parasitic resistance between the n-GaAs contact layer 110 and the n-AlGaAs electron donating layer 116 ) can be obtained.
  • FIG. 3 shows a conduction band diagram of the HEMT acquired by the manufacturing method for a semiconductor device according to this embodiment.
  • the solid line indicates the band of this embodiment having an InAlGaAs layer (which is the In 2.2 Al 0.2 Ga 0.6 As layer) as an etching stopper layer
  • the dotted line indicates a conventional band having an AlGaAs layer as an etching stopper layer.
  • an InAlGaAs layer (which is the In 0.2 Al 0.2 Ga 0.6 As layer) functioning as an etching stopper layer and two GaAs layers (which are the n-GaAs contact layer 110 and the undoped-GaAs gate buried layer 114 ) sandwiching the InAlGaAs layer form substantially flat bands in the conduction band.
  • the AlGaAs layer functioning as an etching stopper layer and two GaAs layers (which are the n-GaAs contact layer 110 and the undoped-GaAs gate buried layer 114 ) sandwiching the AlGaAs layer form largely varying bands in the conduction band, resulting in a discontinuous conduction band.
  • the conduction band diagram shown in FIG. 3 shows that, according to this embodiment, the electrons from the n-GaAs contact layer 110 can be easily conducted because the barrier caused by the conduction band discontinuity due to the etching stopper layer is low, and the increase in contact resistance is suppressed.
  • FIG. 4 shows changes in etching rates of an In AlGaAs layer and an AlGaAs layer according to the composition ratios thereof (where the composition ratio 0% is the etching rate of a GaAs layer).
  • the composition ratio 0% is the etching rate of a GaAs layer.
  • the etching rate is 1/50 or lower with respect to the GaAs layer, which means that the InAlGaAs layer can sufficiently function as an etching stopper layer.
  • the n-GaAs contact layer 110 (which is the second GaAs layer) and the InAlGaAs etching stopper layer 112 are etched by using as an etchant a mixed solution of an organic acid or a organic salt, oxygenated water and water.
  • the mixed solution as the etchant for etching the GaAs contact layer 110 (which is the second GaAs layer) can contribute to etching with high precision because the etching rate against the InAlGaAs etching stopper layer 112 is 1/50 or lower (preferably, 1/100 or lower) of that against the n-GaAs contact layer 110 (which is the second GaAs layer).
  • the etchant for etching the n-GaAs contact layer 110 is an etchant with the etching rate against the InAlGaAs etching stopper layer 112 being equal to 1/50 or lower (preferably, 1/100 or lower) of the etching rate against the n-GaAs contact layer 110 (which is the second GaAs layer).
  • the etchant to be used for the etching is preferably a mixed solution of an organic acid or an organic salt, oxygenated water and water, and the pH may be 7 to 8 (about 7.5).
  • the organic acid or organic salt may be citric acid and tri-ammonium citrate for etching the n-GaAs contact layer 110 and may be, for example, a mixed solution of phosphoric acid, etcoxygenated water and water for etching the InAlGaAs etching stopper layer 112 .
  • the organic salt may be plural kinds of mixed salt.
  • the mixing ratio of a mixed solution of the organic acid or the organic salt, oxygenated water and water may be 2 g:20 cc:2000 cc to 200 g:20 cc:2000 cc (more preferably 25.3 g:20 cc:2000 cc) when the organic salt is tri-ammonium citrate.
  • the undoped-GaAs gate buried layer 114 may be an AlGaAs gate buried layer containing a low level (15% or lower) of Al.
  • the same manufacturing method as that using a GaAs gate buried layer can reduce the leak current to the undoped-GaAs gate buried layer 114 .
  • the invention is not limited thereto.
  • Layers having separate functions as an electron donating layer and a Schottky layer may be provided. More specifically, a lightly-doped n-AlGaAs Schottky layer (or undoped-AlGaAs Schottky layer) may be provided between the undoped-GaAs gate buried layer 114 and the n-AlGaAs electron donating layer 116 .
  • FIGS. 5 and 6 a manufacturing method for a semiconductor device according to a second embodiment will be explained.
  • the manufacturing method for the semiconductor device according to the second embodiment is also a method for manufacturing an AlGaAs/InGaAs HEMT with a double recess structure, for example.
  • vapor deposition is used to form epitaxial layers on a GaAs substrate 228 .
  • the epitaxial layers are formed by epitaxial growth to include, from the uppermost layer side, an n-GaAs contact layer 210 (500 ⁇ thick), an undoped-Al 0.25 Ga 0.75 As gate buried layer 214 (200 ⁇ thick, which is a second AlGaAs layer and will be called undoped-AlGaAs gate buried layer 214 below), an In 0.5 Al 0.5 As etching stopper layer 212 (20 ⁇ thick, which will be called InAlAs etching stopper layer 212 below), an n-Al 0.25 Ga 0.75 As electron donating layer 216 (250 ⁇ thick, which is a first AlGaAs layer and will be called n-AlGaAs electron donating layer 216 ), an undoped-Al 0.25 Ga 0.75 As spacer layer 218 (30 ⁇ thick),
  • vacuum evaporation and/or the sputtering method is used to form two ohmic electrodes on the n-GaAs contact layer 210 , which are used as a source electrode 230 A and a drain electrode 230 B.
  • photolithography is used to provide a photoresist (not shown) having an opening pattern on the n-GaAs contact layer 210 .
  • selective etching using a mixed solution (etchant) of di-ammonium hydrogen citrate or tri-ammonium citrate, oxygenated water and water is performed on the n-GaAs contact layer 210 between the source electrode 230 A and the drain electrode 230 B to form a wide recess 232 (which is a first through hole).
  • photolithography is used to provide a photoresist (not shown) having an opening pattern both on the n-GaAs contact layer 210 and on the undoped-AlGaAs gate buried layer 214 exposed by the wide recess 232 .
  • the undoped-AlGaAs gate buried layer 214 is etched by a mixed solution (etchant) of tri-ammonium citrate, oxygenated water and water to form an inner recess (which is a second through hole) which is smaller than the wide recess 232 within the wide recess 232 .
  • the mixing ratio of the mixed solution (etchant) is, for example, tri-ammonium citrate salt/25 g:oxygenated water/40 cc:water/2000 cc.
  • the InAlAs etching stopper layer 212 is little etched because the etching rate of the undoped-AlGaAs gate buried layer 214 is about 1000 ⁇ /min while the etching rate of the InAlAs etching stopper layer 212 is 10 ⁇ /min or lower, for example. Therefore, the InAs etching stopper layer 212 stops the etching.
  • a gate electrode 236 which is imbedded in the inner recess 234 and is also formed on the edge part of the inner recess 234 of the undoped-AlGaAs gate buried layer 214 (that is, on the undoped-AlGaAs gate buried layer 214 around the opening part of the inner recess 234 ).
  • the InAlAs layer (which is the InAlAs etching stopper layer 212 ) is provided between the two AlGaAs layers (which is the undoped-AlGaAs gate buried layer 214 and n-AlGaAs electron donating layer 216 ).
  • the In 0.5 Al 0.5 As layer is used as the InAlAs layer functioning as an etching stopper layer.
  • a ratio of In:Al of the InAlAs etching stopper layer is preferably in a range of of 4:6 to 6:4 (more preferably, 4.5:5.5 to 5.5:4.5).
  • the InAlAs layer functioning as the etching stopper layer has a sufficiently low etching rate with respect to the undoped-AlGaAs gate buried layer 214 (which is the second AlGaAs layer), the InAlAs layer can fully exhibit the function as an etching stopper layer.
  • the InAlAs layer as an etching stopper layer has a sufficiently low barrier against the AlGaAs layers (which are the undoped-AlGaAs gate buried layer 214 and the n-AlGaAs electron donating layer 216 ) in the conduction of electrons, which can suppress the increase in contact resistance.
  • an InAlAs layer containing In can have a sufficiently low barrier against an AlGaAs layer.
  • a threshold thickness at which dislocation does not occur exists and depends on a degree of mismatching with the lattice constant of a base. Therefore, the composition and thickness may not be selected freely.
  • the threshold thickness in this case is about 20 ⁇ .
  • the contact resistance decreases with respect to the AlGaAs layer.
  • the threshold thickness decreases, the thickness providing the sufficient function as an etching stopper layer may not be obtained. Therefore, in this embodiment, the InAlAs layer having the above-mentioned predetermined composition ratio allows lattice matching and can be formed in thickness allowing the sufficient function as an etching stopper layer (more specifically, such as 15 ⁇ or thicker), and the contact resistance can be reduced.
  • the etching stopper layer can be used to perform selective etching with high precision between two AlGaAs layers and can suppress the increase in contact resistance.
  • the etching depth can be controlled with high precision, and a device with a low parasitic resistance (more specifically, such as a device with a low parasitic resistance between the n-GaAs contact layer 210 and the n-AlGaAs electron donating layer 216 ) can be obtained.
  • FIG. 7 shows a conduction band diagram of the HEMT acquired by the manufacturing method for a semiconductor device according to this embodiment.
  • the solid line indicates the band of this embodiment having an InAlAs layer (which is the In 0.5 Al 0.5 As layer) as an etching stopper layer
  • the dotted line indicates a conventional band having an AlAs layer as an etching stopper layer.
  • an InAlAs layer (which is In 0.5 Al 0.5 As layer) functioning as an etching stopper layer and two AlGaAs layers (which are the undoped-AlGaAs gate buried layer 214 and the n-AlGaAs electron donating layer 216 ) sandwiching the InAlAs layer form substantially flat bands in the conduction band.
  • the AlAs layer functioning as an etching stopper layer and two AlGaAs layers (which are the undoped-AlGaAs gate buried layer 214 and the n-AlGaAs electron donating layer 216 ) sandwiching the AlAs layer form largely varying bands in the conduction band, resulting in a discontinuous conduction band.
  • the conduction band diagram shown in FIG. 7 shows that, according to this embodiment, the electrons from the n-GaAs contact layer 210 can be easily conducted because the barrier caused by the conduction band discontinuity due to the etching stopper layer is low, and the increase in contact resistance is suppressed.
  • an AlAs layer or Al x Gal 1 ⁇ x As (x>0.7) layer containing a high level of Al is used in a selective etching with respect to Al x Ga x ⁇ 1 As (0.15 ⁇ x ⁇ 0.35) layer, and the conduction band discontinuity against the Al x Ga x ⁇ 1 As (0.15 ⁇ x ⁇ 0.35) layer can be significantly suppressed low.
  • the ground level of the conduction band of an Al x Ga 1 ⁇ x As (x>0.43) layer is an X point, whereas the ground level of the conduction band of other materials is a ⁇ point. It is known that, when the Al x Ga 1 ⁇ 1 As (x>0.43) layer is remarkably thin, the barrier at the ⁇ point becomes dominant.
  • the n-GaAs contact layer 210 and the undoped-AlGaAs gate buried layer 214 are etched by using as an etchant a mixed solution of an organic acid or a organic salt, oxygenated water and water.
  • the mixed solution as the etchant for etching the undoped-AlGaAs gate buried layer 214 (which is the second AlGaAs layer) can contribute to etching with high precision because the etching rate against the InAlAs etching stopper layer 212 is 1/500 or lower of that against the undoped-AlGaAs gate buried layer 214 (which is the second AlGaAs layer).
  • the etchant for etching the undoped-AlGaAs gate buried layer 214 is an etchant with the etching rate against the InAlAs etching stopper layer 212 being equal to 1/500 or lower of the etching rate against the undoped-AlGaAs gate buried layer 214 (which is the second AlGaAs layer). Because the other preferable characteristics of the etchant are the same as those of the first embodiment, the description thereon will be omitted.
  • the invention is not limited thereto.
  • Layers having separate functions as an electron donating layer and a Schottky layer may be provided. More specifically, a low-doped n-AlGaAs Schottky layer (or undoped-AlGaAs Schottky layer) may be provided between the In 0.5 Al 0.5 As etching stopper layer 212 and the n-AlGaAs electron donating layer 216 .
  • the invention is not limited thereto.
  • the invention is also applicable to a manufacturing method for a semiconductor device (such as a MESFET (or Metal-Semiconductor Field Effect Transistor)) having continuous two GaAs layers or two AlGaAs layers and the interface between the layers to be etched.
  • a semiconductor device such as a MESFET (or Metal-Semiconductor Field Effect Transistor)
  • the invention is also applicable to a manufacturing method for a semiconductor device (or an electronic device) using electrons as conduction carriers.
  • the first embodiment is effective, that is, it is effective to insert an In AlGaAs layer between the layers and perform etching processing.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Junction Field-Effect Transistors (AREA)
  • Weting (AREA)

Abstract

A semiconductor device manufacturing method includes: providing a laminated member in which at least a first GaAs layer, an InAlGaAs layer and a second GaAs layer are laminated on or above a substrate in this order; and etching the second GaAs layer using the InAlGaAs layer as an etching stopper layer. A ratio of In:Al of the InAlGaAs layer is in a range of approximately 4:6 to approximately 6:4 and a ratio of (In+Al):Ga of the InAlGaAs layer is in a range of approximately 1.5:8.5 to approximately 5:5.

Description

    CROSS-REFERENCE TO RELATED APPLICATION
  • This application claims priority under 35 USC 119 from Japanese Patent Application No. 2008-211747 filed on Aug. 20, 2008, the disclosure of which is incorporated by reference herein.
    • BACKGROUND OF THE INVENTION
  • 1. Field of the Invention
  • The present invention relates to a manufacturing method for a semiconductor device, and more particularly, to a manufacturing method for a semiconductor device in order to acquire a HEMT (High electron mobility transistor) or a MESFET (Metal-Semiconductor Field Effect Transistor), for example.
  • 2. Description of the Related Art
  • Hitherto, a semiconductor device has been proposed which has a structure having a through hole called recess in a contact layer and having a gate electrode therein (as in Japanese Patent Application Laid-Open (JP-A) No. 2007-157918, for example).
  • On the other hand, one semiconductor device may have a double recess structure having a small through hole called inner recess within a through hole called wide recess, and having a gate electrode imbedded in the small through hole and also disposed on the edge part thereof (refer to “Low Voltage Operation Power Heterojunction FET with Low on-resistance for Personal Digital Cellular Phones”, TECHNICAL REPORT OF IEICE (The Institute of Electronics, Information and Communication Engineers) ED98-215, MW98-178, ICD98-282 (1999-01), for example). The semiconductor device has an etching stopper layer for performing selective etching. For example, generally in a conventional InGaAs/AlGaAs (GaAs) semiconductor device, in order to use an organic acid-oxygenated water mixed solution or a BCl3/SF6 mixed gas to perform selective etching between two GaAs layers or two AlGaAs layers, an AlGaAs layer having a higher mixing ratio of Al (approximately 20% or higher) or an AlAs layer is used as an etching stopper layer.
  • However, because the AlGaAs layer with the higher mixing ratio of Al or AlAs layer as an etching stopper layer has a larger band gap than that of a GaAs layer or an InGaAs layer, conduction band discontinuity increases. The conduction band discontinuity becomes a barrier against electrons, which increases the contact resistance, for example, and results in a device with a larger parasitic resistance.
  • By the way, as a technology for reducing the contact resistance, methods for lowering the barrier at an interface between layers have been proposed (refer to JP-A Nos. 8-162647, 11-54837 and 2007-157918 for example). However, from the viewpoint of the implementation of etching with high precision, the methods are still not enough, and improvements thereon are being demanded today.
    • SUMMARY OF THE INVENTION
  • Accordingly, it is an object of the present invention to provide a manufacturing method for a semiconductor device, which allows, using an etching stopper layer, performing selective etching with high precision between two GaAs layers or two AlGaAs layers and suppressing the increase in contact resistance.
  • According to a first aspect of the present invention, there is provided a semiconductor device manufacturing method, comprising:
  • providing a laminated member in which at least a first GaAs layer, an InAlGaAs layer and a second GaAs layer are laminated on or above a substrate in this order; and
  • etching the second GaAs layer using the InAlGaAs layer as an etching stopper layer, wherein
  • a ratio of In:Al of the InAlGaAs layer is in a range of approximately 4:6 to approximately 6:4 and a ratio of (In+Al):Ga of the InAlGaAs layer is in a range of approximately 1.5:8.5 to approximately 5:5.
  • According to a second aspect of the present invention, there is provided a semiconductor device manufacturing method, comprising:
  • providing a laminated member in which at least an AlGaAs electron donating layer or an AlGaAs Schottky layer, a GaAs gate-buried layer, an InAlGaAs etching stopper layer, and a GaAs contact layer are laminated on or above a substrate in this order;
  • etching the GaAs contact layer to form a first through hole;
  • etching the InAlGaAs etching stopper layer to form a second through hole having an approximately same size as the first through hole;
  • etching the GaAs gate-buried layer to form a third through hole in the first and second through holes, the third through holes being smaller than the first through hole; and
  • forming an electrode in the first and second thorough holes, wherein a ratio of In:Al of the InAlGaAs etching stopper layer is in a range of approximately 4:6 to approximately 6:4 and a ratio of (In+Al):Ga of the InAlGaAs etching stopper layer is in a range of approximately 1.5:8.5 to approximately 5:5.
  • According to a third aspect of the present invention, there is provided a semiconductor device manufacturing method, comprising:
  • providing a laminated member in which at least a first AlGaAs layer, an InAlAs layer and a second AlGaAs layer are laminated on or above a substrate in this order; and
  • etching the second AlGaAs layer using the InAlAs layer as an etching stopper layer, wherein p a ratio of In:Al of the InAlAs layer is in a range of approximately 4:6 to approximately 6:4.
  • According to a fourth aspect of the present invention, there is provided a semiconductor device manufacturing method, comprising:
  • providing a laminated member in which at least an AlGaAs electron donating layer or an AlGaAs Schottky layer, an InAlGaAs etching stopper layer, an AlGaAs gate-buried layer, and a GaAs contact layer are laminated on or above a substrate in this order;
  • etching the GaAs contact layer to form a first through hole;
  • etching the AlGaAs gate-buried layer to form a second through hole in the first through hole, the second through hole being smaller than the first through hole;
  • etching the InAlAs etching stopper layer to form a third through hole having an approximately same size as the second through hole; and
  • filling the second and third through holes in the first through hole to form an electrode, wherein
  • a ratio of In:Al of the InAlGaAs etching stopper layer is in a range of approximately 4:6 to approximately 6:4.
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein:
  • FIG. 1 is a schematic cross-sectional view for explaining a manufacturing process for a semiconductor device according to a first embodiment;
  • FIGS. 2A to 2E are process charts for explaining the manufacturing process for the semiconductor device according to the first embodiment;
  • FIG. 3 is a schematic diagram showing a conduction band of an HEMT acquired by the manufacturing method for the semiconductor device according to the first embodiment;
  • FIG. 4 is a diagram showing changes in etching rate according to the composition ratios of an In AlGaAs layer and an AlGaAs layer;
  • FIG. 5 is a schematic cross-sectional view for explaining a manufacturing process for a semiconductor device according to a second embodiment;
  • FIGS. 6A to 6E are process charts for explaining the manufacturing process for the semiconductor device according to the second embodiment; and
  • FIG. 7 is a schematic diagram showing a conduction band of an HEMT acquired by the manufacturing method for a semiconductor device according to the second embodiment.
    •  DETAILED DESCRIPTION
  • With reference to drawings, preferred embodiments of the present invention will be described below. The same reference numerals are given to those having substantially the same functions throughout all drawings for explanation, and descriptions thereon may be omitted in some cases.
    • First Embodiment
  • Referring to FIGS. 1 and 2, a manufacturing method for a semiconductor device according to a first embodiment will be explained.
  • The manufacturing method for the semiconductor device according to the first embodiment is a method for manufacturing an AlGaAs/InGaAs HEMT with a double recess structure, for example.
  • First of all, more specifically, as shown in FIG. 1, vapor deposition is used to form epitaxial layers on a GaAs substrate 128. The epitaxial layers are formed by epitaxial growth to include, from the uppermost layer side, an n-GaAs contact layer 110 (500 Å thick, which is a second GaAs layer), an In0.2Al0.2Ga0.6As etching stopper layer 112 (100 Å thick, which will be called InAlGaAs etching stopper layer 112 below), an undoped-GaAs gate buried layer 114 (200 Å thick, which is a first GaAs layer), an n-AlGaAs electron donating layer 116 (250 Å thick), an undoped-Al0.25Ga0.75As spacer layer 118 (30 Å thick), an In0.2Ga0.8As channel layer 120 (100 Å thick), an undoped-Al0.25Ga0.75As spacer layer 122 (50 Å thick), an n-Al0.25Ga0.75As electron donating layer 124 (70 Å thick), and an undoped-Al0.25Ga0.75As buffer layer 126 (2000 Å thick). The n-AlGaAs electron donating layer 216 is a layer functioning both as an electron donating layer and a Schottky layer.
  • Next, as shown in FIG. 2A, vacuum evaporation and/or the sputtering method is used to form two ohmic electrodes on the n-GaAs contact layer 110, which are used as a source electrode 130A and a drain electrode 130B.
  • Next, as shown in FIG. 2B, photolithography is used to provide a photoresist (not shown) having an opening pattern on the n-GaAs contact layer 110. Then, selective etching using a mixed solution (etchant) of tri-ammonium citrate, oxygenated water and water is performed on the n-GaAs contact layer 110 between the source electrode 130A and the drain electrode 130B to form a wide recess 132 (which is a first through hole). The mixing ratio of the mixed solution (etchant) is, for example, tri-ammonium citrate salt/25 g:oxygenated water/40 cc:water/2000 cc.
  • In the etching process, the InAlGaAs etching stopper layer 112 is little etched because the etching rate of the n-GaAs contact layer 110 is about 1000 Å/min while the etching rate of the InAlGaAs etching stopper layer 112 is 10 Å/min or lower, for example. Therefore, the InAlGaAs etching stopper layer 112 stops the etching.
  • Next, as shown in FIG. 2C, by keeping the photoresist, a mixed solution (which is an etchant a nonselective etchant) of phosphoric acid, oxygenated water and water, for example, is used to perform nonselective etching (uniform etching) on the InAlGaAs etching stopper layer 112, whereby making a wide recess 132 reach the undoped-GaAs gate buried layer 114. The mixing ratio of the mixed solution (etchant) is phosphoric acid/100 cc:oxygenated water/5 cc:water/2100 cc. The depth of the wide recess 132 as a result of the etching on the InAlGaAs etching stopper layer 112 corresponds to a second through hole.
  • The etching is not required to reach the undoped-GaAs gate buried layer 114, but the etching may be stopped on the way. Then, after a photoresist (not shown) for forming an inner recess 134, which will be described later, is provided, the InAlGaAs etching stopper layer 112 remaining on the undoped-GaAs gate buried layer 114 may be removed by etching.
  • Next, as shown in FIG. 2D, photolithography is used to provide a photoresist (not shown) having an opening pattern both on the n-GaAs contact layer 110 and on the undoped-GaAs gate buried layer 114 exposed by the wide recess 132. Then, by performing selective etching, the inner recess 134 (which is a third through hole), which is smaller than the wide recess 132, is formed within the wide recess 132. The selective etching stops at the n-AlGaAs electron donating layer 116.
  • Next, as shown in FIG. 2E, aluminum (Al) of 5000 Å thick is deposited using vacuum evaporation or sputtering, for example, and then the aluminum is lifted off to form a gate electrode 136, which is imbedded in the inner recess 134 and is also formed on the edge part of the inner recess 134 of the undoped-GaAs gate buried layer 114 (that is, on the undoped-GaAs gate buried layer 114 around the opening part of the inner recess 134).
  • In this way, the AlGaAs/InGaAs HEMT with a double recess structure is manufactured.
  • In the manufacturing method for the semiconductor device according to this embodiment which has been described above, the InAlGaAs layer (which is the InAlGaAs etching stopper layer 112) is provided between the two GaAs layers (which is the n-GaAs contact layer 110 and the undoped-GaAs gate buried layer 114).
  • In addition, in this embodiment, the In0.2Al0.2Ga0.6As layer is used as the InAlGaAs layer functioning as an etching stopper layer. A ratio of In:Al of the InAlGaAs etching stopper layer is preferably in a range of 4:6 to 6:4, and a ratio of (In+Al):Ga of the InAlGaAs etching stopper layer is preferably in a range of 1.5:8.5 to 5:5.
  • Because the InAlGaAs layer functioning as the etching stopper layer has a sufficiently low etching rate with respect to the n-GaAs contact layer 110 (which is the second GaAs layer), the InAlGaAs layer can fully exhibit the function as an etching stopper layer.
  • On the other hand, the InAlGaAs layer as an etching stopper layer has a sufficiently low barrier against the GaAs layers (which are the n-GaAs contact layer 110 and the undoped-GaAs gate buried layer 114) in the conduction of electrons, which can suppress the increase in contact resistance.
  • Here, an InAlGaAs layer containing In can have a sufficiently low barrier against an GaAs layer. However, because an InAlGaAs layer is a nonlattice matching layer, a threshold thickness at which dislocation does not occur (that is, the upper limit of thickness with which a layer having lattice matching as a result of epitaxial growth with good crystal can be obtained) exists and depends on a degree of mismatching with the lattice constant of a base. Therefore, the composition and thickness may not be selected freely. For example, according to this embodiment, the In0.2Al0.2Ga0.6As layer has a composition ratio of In of 20% (In+Al+Ga=100%). The threshold thickness in this case is about 130 Å. As the composition ratio of In increases, the contact resistance decreases with respect to the GaAs layer. On the other hand, because the threshold thickness decreases, the thickness providing the sufficient function as an etching stopper layer may not be obtained. Therefore, in this embodiment, the InAlGaAs layer having the above-mentioned predetermined composition ratio allows lattice matching and can be formed in thickness allowing the sufficient function as an etching stopper layer (more specifically, such as 100 Å or thicker), and the contact resistance can be reduced.
  • Therefore, the InAlGaAs layer having the above-mentioned predetermined composition can be used as an etching stopper layer to perform selective etching with high precision between two GaAs layers and can suppress the increase in contact resistance. As a result, the etching depth can be controlled with high precision, and a device with a low parasitic resistance (more specifically, such as a device with a low parasitic resistance between the n-GaAs contact layer 110 and the n-AlGaAs electron donating layer 116) can be obtained.
  • Here, FIG. 3 shows a conduction band diagram of the HEMT acquired by the manufacturing method for a semiconductor device according to this embodiment. In the conduction band diagram in FIG. 3, the solid line indicates the band of this embodiment having an InAlGaAs layer (which is the In2.2Al0.2Ga0.6As layer) as an etching stopper layer, and the dotted line indicates a conventional band having an AlGaAs layer as an etching stopper layer. As shown in FIG. 3, according to this embodiment, an InAlGaAs layer (which is the In0.2Al0.2Ga0.6As layer) functioning as an etching stopper layer and two GaAs layers (which are the n-GaAs contact layer 110 and the undoped-GaAs gate buried layer 114) sandwiching the InAlGaAs layer form substantially flat bands in the conduction band. On the other hand, conventionally, the AlGaAs layer functioning as an etching stopper layer and two GaAs layers (which are the n-GaAs contact layer 110 and the undoped-GaAs gate buried layer 114) sandwiching the AlGaAs layer form largely varying bands in the conduction band, resulting in a discontinuous conduction band.
  • In this way, the conduction band diagram shown in FIG. 3 shows that, according to this embodiment, the electrons from the n-GaAs contact layer 110 can be easily conducted because the barrier caused by the conduction band discontinuity due to the etching stopper layer is low, and the increase in contact resistance is suppressed.
  • FIG. 4 shows changes in etching rates of an In AlGaAs layer and an AlGaAs layer according to the composition ratios thereof (where the composition ratio 0% is the etching rate of a GaAs layer). As shown in FIG. 4, in the case of an InAlGaAs layer, for example, when the In+Al ratio is 15%, the etching rate is 1/50 or lower with respect to the GaAs layer, which means that the InAlGaAs layer can sufficiently function as an etching stopper layer.
  • In the manufacturing method for the semiconductor device according to this embodiment, the n-GaAs contact layer 110 (which is the second GaAs layer) and the InAlGaAs etching stopper layer 112 are etched by using as an etchant a mixed solution of an organic acid or a organic salt, oxygenated water and water. In particular, the mixed solution as the etchant for etching the GaAs contact layer 110 (which is the second GaAs layer) can contribute to etching with high precision because the etching rate against the InAlGaAs etching stopper layer 112 is 1/50 or lower (preferably, 1/100 or lower) of that against the n-GaAs contact layer 110 (which is the second GaAs layer).
  • In other words, it is preferable that the etchant for etching the n-GaAs contact layer 110 (which is the second GaAs layer) is an etchant with the etching rate against the InAlGaAs etching stopper layer 112 being equal to 1/50 or lower (preferably, 1/100 or lower) of the etching rate against the n-GaAs contact layer 110 (which is the second GaAs layer).
  • Here, the etchant to be used for the etching is preferably a mixed solution of an organic acid or an organic salt, oxygenated water and water, and the pH may be 7 to 8 (about 7.5).
  • The organic acid or organic salt may be citric acid and tri-ammonium citrate for etching the n-GaAs contact layer 110 and may be, for example, a mixed solution of phosphoric acid, etcoxygenated water and water for etching the InAlGaAs etching stopper layer 112. The organic salt may be plural kinds of mixed salt.
  • In an etchant to be used for the etching, the mixing ratio of a mixed solution of the organic acid or the organic salt, oxygenated water and water may be 2 g:20 cc:2000 cc to 200 g:20 cc:2000 cc (more preferably 25.3 g:20 cc:2000 cc) when the organic salt is tri-ammonium citrate.
  • In the manufacturing method for a semiconductor device according to this embodiment, the undoped-GaAs gate buried layer 114 may be an AlGaAs gate buried layer containing a low level (15% or lower) of Al. Thus, the same manufacturing method as that using a GaAs gate buried layer can reduce the leak current to the undoped-GaAs gate buried layer 114.
  • Having described the manufacturing method for the semiconductor device according to this embodiment in which the layer functioning as both an electron donating layer and a Schottky layer is applied as the n-AlGaAs electron donating layer 116, the invention is not limited thereto. Layers having separate functions as an electron donating layer and a Schottky layer may be provided. More specifically, a lightly-doped n-AlGaAs Schottky layer (or undoped-AlGaAs Schottky layer) may be provided between the undoped-GaAs gate buried layer 114 and the n-AlGaAs electron donating layer 116.
    • Second Embodiment
  • Referring to FIGS. 5 and 6, a manufacturing method for a semiconductor device according to a second embodiment will be explained.
  • The manufacturing method for the semiconductor device according to the second embodiment is also a method for manufacturing an AlGaAs/InGaAs HEMT with a double recess structure, for example.
  • First of all, more specifically, as shown in FIG. 5, vapor deposition is used to form epitaxial layers on a GaAs substrate 228. The epitaxial layers are formed by epitaxial growth to include, from the uppermost layer side, an n-GaAs contact layer 210 (500 Å thick), an undoped-Al0.25Ga0.75As gate buried layer 214 (200 Å thick, which is a second AlGaAs layer and will be called undoped-AlGaAs gate buried layer 214 below), an In0.5Al0.5As etching stopper layer 212 (20 Å thick, which will be called InAlAs etching stopper layer 212 below), an n-Al0.25Ga0.75As electron donating layer 216 (250 Å thick, which is a first AlGaAs layer and will be called n-AlGaAs electron donating layer 216), an undoped-Al0.25Ga0.75As spacer layer 218 (30 Å thick), an In0.2Ga0.8As channel layer 220 (100 Å thick), an undoped-Al0.25Ga0.75As spacer layer 222 (50 Å thick), an n-Al0.25Ga0.75As electron donating layer 224 (70 Å thick), and an undoped-Al0.25Ga0.75As buffer layer 226 (2000 Å thick). The n-AlGaAs electron donating layer 216 is a layer functioning both as an electron donating layer and a Schottky layer.
  • Next, as shown in FIG. 6A, vacuum evaporation and/or the sputtering method is used to form two ohmic electrodes on the n-GaAs contact layer 210, which are used as a source electrode 230A and a drain electrode 230B.
  • Next, as shown in FIG. 6B, photolithography is used to provide a photoresist (not shown) having an opening pattern on the n-GaAs contact layer 210. Then, selective etching using a mixed solution (etchant) of di-ammonium hydrogen citrate or tri-ammonium citrate, oxygenated water and water is performed on the n-GaAs contact layer 210 between the source electrode 230A and the drain electrode 230B to form a wide recess 232 (which is a first through hole).
  • Next, as shown in FIG. 6C, photolithography is used to provide a photoresist (not shown) having an opening pattern both on the n-GaAs contact layer 210 and on the undoped-AlGaAs gate buried layer 214 exposed by the wide recess 232. Then, the undoped-AlGaAs gate buried layer 214 is etched by a mixed solution (etchant) of tri-ammonium citrate, oxygenated water and water to form an inner recess (which is a second through hole) which is smaller than the wide recess 232 within the wide recess 232. The mixing ratio of the mixed solution (etchant) is, for example, tri-ammonium citrate salt/25 g:oxygenated water/40 cc:water/2000 cc.
  • In the etching process, the InAlAs etching stopper layer 212 is little etched because the etching rate of the undoped-AlGaAs gate buried layer 214 is about 1000 Å/min while the etching rate of the InAlAs etching stopper layer 212 is 10 Å/min or lower, for example. Therefore, the InAs etching stopper layer 212 stops the etching.
  • Next, as shown in FIG. 6D, by keeping the photoresist (which is the photoresist for forming the inner recess), slight etching is performed on the InAlAs etching stopper layer 212 by using a dilute hydrochloric acid solution, whereby an inner recess 234 reachs the n-AlGaAs electron donating layer 216. The depth of the inner recess 234 as a result of the etching on the InAlAs etching stopper layer 212 corresponds to a third through hole.
  • Next, as shown in FIG. 6E, aluminum (Al) of 5000 Å thick is deposited using vacuum evaporation or sputtering, for example, and then the aluminum is lifted off to form a gate electrode 236, which is imbedded in the inner recess 234 and is also formed on the edge part of the inner recess 234 of the undoped-AlGaAs gate buried layer 214 (that is, on the undoped-AlGaAs gate buried layer 214 around the opening part of the inner recess 234).
  • In this way, the AlGaAs/InGaAs HEMT with a double recess structure is manufactured.
  • In the manufacturing method for the semiconductor device according to this embodiment which has been described above, the InAlAs layer (which is the InAlAs etching stopper layer 212) is provided between the two AlGaAs layers (which is the undoped-AlGaAs gate buried layer 214 and n-AlGaAs electron donating layer 216).
  • In addition, in this embodiment, the In0.5Al0.5As layer is used as the InAlAs layer functioning as an etching stopper layer. A ratio of In:Al of the InAlAs etching stopper layer is preferably in a range of of 4:6 to 6:4 (more preferably, 4.5:5.5 to 5.5:4.5).
  • Because the InAlAs layer functioning as the etching stopper layer has a sufficiently low etching rate with respect to the undoped-AlGaAs gate buried layer 214 (which is the second AlGaAs layer), the InAlAs layer can fully exhibit the function as an etching stopper layer.
  • On the other hand, the InAlAs layer as an etching stopper layer has a sufficiently low barrier against the AlGaAs layers (which are the undoped-AlGaAs gate buried layer 214 and the n-AlGaAs electron donating layer 216) in the conduction of electrons, which can suppress the increase in contact resistance.
  • Here, an InAlAs layer containing In can have a sufficiently low barrier against an AlGaAs layer. However, because an InAlAs layer is a nonlattice matching layer, a threshold thickness at which dislocation does not occur (that is, the upper limit of thickness with which a layer having lattice matching as a result of epitaxial growth with good crystal can be obtained) exists and depends on a degree of mismatching with the lattice constant of a base. Therefore, the composition and thickness may not be selected freely. For example, according to this embodiment, the In0.5Al0.5As layer has a composition ratio of In of 50% (In+Al=100%). The threshold thickness in this case is about 20 Å. As the composition ratio of In increases, the contact resistance decreases with respect to the AlGaAs layer. On the other hand, because the threshold thickness decreases, the thickness providing the sufficient function as an etching stopper layer may not be obtained. Therefore, in this embodiment, the InAlAs layer having the above-mentioned predetermined composition ratio allows lattice matching and can be formed in thickness allowing the sufficient function as an etching stopper layer (more specifically, such as 15 Å or thicker), and the contact resistance can be reduced.
  • Therefore, the etching stopper layer can be used to perform selective etching with high precision between two AlGaAs layers and can suppress the increase in contact resistance. As a result, the etching depth can be controlled with high precision, and a device with a low parasitic resistance (more specifically, such as a device with a low parasitic resistance between the n-GaAs contact layer 210 and the n-AlGaAs electron donating layer 216) can be obtained.
  • Here, FIG. 7 shows a conduction band diagram of the HEMT acquired by the manufacturing method for a semiconductor device according to this embodiment. In the conduction band diagram in FIG. 7, the solid line indicates the band of this embodiment having an InAlAs layer (which is the In0.5Al0.5As layer) as an etching stopper layer, and the dotted line indicates a conventional band having an AlAs layer as an etching stopper layer. As shown in FIG. 7, according to this embodiment, an InAlAs layer (which is In0.5Al0.5As layer) functioning as an etching stopper layer and two AlGaAs layers (which are the undoped-AlGaAs gate buried layer 214 and the n-AlGaAs electron donating layer 216) sandwiching the InAlAs layer form substantially flat bands in the conduction band. On the other hand, conventionally, the AlAs layer functioning as an etching stopper layer and two AlGaAs layers (which are the undoped-AlGaAs gate buried layer 214 and the n-AlGaAs electron donating layer 216) sandwiching the AlAs layer form largely varying bands in the conduction band, resulting in a discontinuous conduction band.
  • In this way, the conduction band diagram shown in FIG. 7 shows that, according to this embodiment, the electrons from the n-GaAs contact layer 210 can be easily conducted because the barrier caused by the conduction band discontinuity due to the etching stopper layer is low, and the increase in contact resistance is suppressed.
  • Giving a supplementary explanation, normally, an AlAs layer or AlxGal1−xAs (x>0.7) layer containing a high level of Al is used in a selective etching with respect to AlxGax−1As (0.15<x<0.35) layer, and the conduction band discontinuity against the AlxGax−1As (0.15<x<0.35) layer can be significantly suppressed low. However, the ground level of the conduction band of an AlxGa1−xAs (x>0.43) layer is an X point, whereas the ground level of the conduction band of other materials is a Γ point. It is known that, when the AlxGa1−1As (x>0.43) layer is remarkably thin, the barrier at the Γ point becomes dominant. Therefore, the conduction band discontinuity at the Γ point must be taken into consideration. From the viewpoint of this, for example, it should be considered that the conduction band discontinuity of the AlAs layer against the AlxGax−1As (x=0.25) layer is the order of 1 eV.
  • In the manufacturing method for the semiconductor device according to this embodiment, the n-GaAs contact layer 210 and the undoped-AlGaAs gate buried layer 214 (which is the second AlGaAs layer) are etched by using as an etchant a mixed solution of an organic acid or a organic salt, oxygenated water and water. In particular, the mixed solution as the etchant for etching the undoped-AlGaAs gate buried layer 214 (which is the second AlGaAs layer) can contribute to etching with high precision because the etching rate against the InAlAs etching stopper layer 212 is 1/500 or lower of that against the undoped-AlGaAs gate buried layer 214 (which is the second AlGaAs layer).
  • In other words, it is preferable that the etchant for etching the undoped-AlGaAs gate buried layer 214 (which is the second AlGaAs layer) is an etchant with the etching rate against the InAlAs etching stopper layer 212 being equal to 1/500 or lower of the etching rate against the undoped-AlGaAs gate buried layer 214 (which is the second AlGaAs layer). Because the other preferable characteristics of the etchant are the same as those of the first embodiment, the description thereon will be omitted.
  • Having described the manufacturing method for the semiconductor device according to this embodiment in which the layer functioning as both an electron donating layer and a Schottky layer is applied as the n-AlGaAs electron donating layer 216, the invention is not limited thereto. Layers having separate functions as an electron donating layer and a Schottky layer may be provided. More specifically, a low-doped n-AlGaAs Schottky layer (or undoped-AlGaAs Schottky layer) may be provided between the In0.5Al0.5As etching stopper layer 212 and the n-AlGaAs electron donating layer 216.
  • Having described the manufacturing methods for the semiconductor device according to the embodiments in which an HEMT is manufactured, the invention is not limited thereto. The invention is also applicable to a manufacturing method for a semiconductor device (such as a MESFET (or Metal-Semiconductor Field Effect Transistor)) having continuous two GaAs layers or two AlGaAs layers and the interface between the layers to be etched. Alternatively, the invention is also applicable to a manufacturing method for a semiconductor device (or an electronic device) using electrons as conduction carriers. More specifically, for example, in order to perform etching with high precision on the interface between an undoped-GaAs layer and an n-GaAs layer, the first embodiment is effective, that is, it is effective to insert an In AlGaAs layer between the layers and perform etching processing.
  • Although various exemplary embodiments have been shown and described, the invention is not limited to the embodiments shown. Therefore, the scope of the invention is intended to be limited solely by the scope of the claims that follow.

Claims (13)

1. A semiconductor device manufacturing method, comprising:
providing a laminated member in which at least a first GaAs layer, an InAlGaAs layer and a second GaAs layer are laminated on or above a substrate in this order; and
etching the second GaAs layer using the InAlGaAs layer as an etching stopper layer, wherein
a ratio of In:Al of the InAlGaAs layer is in a range of approximately 4:6 to approximately 6:4 and a ratio of (In+Al):Ga of the InAlGaAs layer is in a range of approximately 1.5:8.5 to approximately 5:5.
2. A semiconductor device manufacturing method according to claim 1, wherein an etchant used in the etching is a mixed liquid of an organic acid or a salt thereof, oxygenated water and water.
3. A semiconductor device manufacturing method according to claim 1, wherein an etchant used in the etching is an etchant with which an etching rate of the InAlGaAs layer is equal to or less than 1/50 of an etching rate of the second GaAs layer.
4. A semiconductor device manufacturing method, comprising:
providing a laminated member in which at least an AlGaAs electron donating layer or an AlGaAs Schottky layer, a GaAs gate-buried layer, an InAlGaAs etching stopper layer, and a GaAs contact layer are laminated on or above a substrate in this order;
etching the GaAs contact layer to form a first through hole;
etching the InAlGaAs etching stopper layer to form a second through hole having approximately the same size as the first through hole;
etching the GaAs gate-buried layer to form a third through hole in the first and second through holes, the third through hole being smaller than the first through hole; and
forming an electrode in the first and second through holes, wherein
a ratio of In:Al of the InAlGaAs etching stopper layer is in a range of approximately 4:6 to approximately 6:4 and a ratio of (In+Al):Ga of the InAlGaAs etching stopper layer is in a range of approximately 1.5:8.5 to approximately 5:5.
5. A semiconductor device manufacturing method according to claim 4, wherein an etchant for etching the GaAs contact layer is a mixed liquid of an organic acid or a salt thereof, oxygenated water and water.
6. A semiconductor device manufacturing method according to claim 4, wherein an etchant for etching the GaAs contact layer is an etchant with which an etching rate of the InAlGaAs etching stopper layer is equal to or less than 1/50 of an etching rate of the GaAs contact layer.
7. A semiconductor device manufacturing method according to claim 4, wherein the GaAs gate-buried layer is an undoped GaAs gate-buried layer or an AlGaAs gate-buried layer including Al at a low concentration.
8. A semiconductor device manufacturing method, comprising:
providing a laminated member in which at least a first AlGaAs layer, an InAlAs layer and a second AlGaAs layer are laminated on or above a substrate in this order; and
etching the second AlGaAs layer using the InAlAs layer as an etching stopper layer, wherein
a ratio of In:Al of the InAlAs layer is in a range of approximately 4:6 to approximately 6:4.
9. A semiconductor device manufacturing method according to claim 8, wherein an etchant used in the etching is a mixed liquid of an organic acid or a salt thereof, oxygenated water and water.
10. A semiconductor device manufacturing method according to claim 8, wherein an etchant used in the etching is an etchant with which an etching rate of the InAlAs layer is equal to or less than 1/500 of an etching rate of the second AlGaAs layer.
11. A semiconductor device manufacturing method, comprising:
providing a laminated member in which at least an AlGaAs electron donating layer or an AlGaAs Schottky layer, an InAlGaAs etching stopper layer, an AlGaAs gate-buried layer, and a GaAs contact layer are laminated on or above a substrate in this order;
etching the GaAs contact layer to form a first through hole;
etching the AlGaAs gate-buried layer to form a second through hole in the first through hole, the second through hole being smaller than the first through hole;
etching the InAlAs etching stopper layer to form a third through hole having approximately the same size as the second through hole; and
filling the second and third through holes in the first through hole to form an electrode, wherein
a ratio of In:Al of the InAlGaAs etching stopper layer is in a range of approximately 4:6 to approximately 6:4.
12. A semiconductor device manufacturing method according to claim 11, wherein an etchant used in the etching of the InGaAs gate-buried layer is a mixed liquid of an organic acid or a salt thereof, oxygenated water and water.
13. A semiconductor device manufacturing method according to claim 11, wherein an etchant used in the etching of the AlGaAs gate-buried layer is an etchant with which an etching rate of the InAlAs etching stopper layer is equal to or less than 1/500 of an etching rate of the AlGaAs gate-buried layer.
US12/461,577 2008-08-20 2009-08-17 Semiconductor device manufacturing method Expired - Fee Related US7981787B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2008211747A JP2010050204A (en) 2008-08-20 2008-08-20 Method of manufacturing semiconductor element
JP2008-211747 2008-08-20

Publications (2)

Publication Number Publication Date
US20100048016A1 true US20100048016A1 (en) 2010-02-25
US7981787B2 US7981787B2 (en) 2011-07-19

Family

ID=41696778

Family Applications (1)

Application Number Title Priority Date Filing Date
US12/461,577 Expired - Fee Related US7981787B2 (en) 2008-08-20 2009-08-17 Semiconductor device manufacturing method

Country Status (2)

Country Link
US (1) US7981787B2 (en)
JP (1) JP2010050204A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20180209049A1 (en) * 2017-01-23 2018-07-26 Versum Materials Us, Llc Etching Solution For Tungsten And GST Films
US10988405B2 (en) 2013-08-15 2021-04-27 Corning Incorporated Intermediate to high CTE glasses and glass articles comprising the same
USRE49307E1 (en) 2013-08-15 2022-11-22 Corning Incorporated Alkali-doped and alkali-free boroaluminosilicate glass

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011111443A1 (en) 2010-03-08 2011-09-15 日本電気株式会社 Mobile communication terminal apparatus, method for controlling power consumption of mobile communication terminal apparatus, and recording medium

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5844260A (en) * 1992-10-09 1998-12-01 Fujitsu Limited Compound semiconductor device constructed on a heteroepitaxial substrate
US20040082158A1 (en) * 2002-10-24 2004-04-29 Whelan Colin S. Method of forming a self-aligned, selectively etched, double recess high electron mobility transistor
US7012286B2 (en) * 2001-09-27 2006-03-14 Murata Manufacturing Co., Ltd. Heterojunction field effect transistor
US7705377B2 (en) * 2005-09-30 2010-04-27 Oki Semiconductor Co., Ltd. Field effect transistor comprising compound semiconductor

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0209194B1 (en) * 1985-07-15 1991-04-17 Koninklijke Philips Electronics N.V. Method of manufacturing a semiconductor device, in which a layer of gallium arsenide is etched in a basic solution of hydrogen peroxide
JP2679653B2 (en) 1994-12-05 1997-11-19 日本電気株式会社 Semiconductor device
JP3779040B2 (en) 1997-07-29 2006-05-24 富士通株式会社 Optical semiconductor device and manufacturing method thereof
JP2007157918A (en) 2005-12-02 2007-06-21 Toshiba Corp Semiconductor device and manufacturing method therefor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5844260A (en) * 1992-10-09 1998-12-01 Fujitsu Limited Compound semiconductor device constructed on a heteroepitaxial substrate
US7012286B2 (en) * 2001-09-27 2006-03-14 Murata Manufacturing Co., Ltd. Heterojunction field effect transistor
US20040082158A1 (en) * 2002-10-24 2004-04-29 Whelan Colin S. Method of forming a self-aligned, selectively etched, double recess high electron mobility transistor
US7705377B2 (en) * 2005-09-30 2010-04-27 Oki Semiconductor Co., Ltd. Field effect transistor comprising compound semiconductor

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10988405B2 (en) 2013-08-15 2021-04-27 Corning Incorporated Intermediate to high CTE glasses and glass articles comprising the same
US11168018B2 (en) 2013-08-15 2021-11-09 Corning Incorporated Aluminoborosilicate glass substantially free of alkali oxides
USRE49307E1 (en) 2013-08-15 2022-11-22 Corning Incorporated Alkali-doped and alkali-free boroaluminosilicate glass
US20180209049A1 (en) * 2017-01-23 2018-07-26 Versum Materials Us, Llc Etching Solution For Tungsten And GST Films
US11035044B2 (en) * 2017-01-23 2021-06-15 Versum Materials Us, Llc Etching solution for tungsten and GST films

Also Published As

Publication number Publication date
US7981787B2 (en) 2011-07-19
JP2010050204A (en) 2010-03-04

Similar Documents

Publication Publication Date Title
US9837518B2 (en) Semiconductor device
US8907349B2 (en) Semiconductor device and method of manufacturing the same
EP2306500B1 (en) Compound semiconductor device and method of manufacturing the same
US9728613B2 (en) High electron mobility transistor structure
US8441035B2 (en) Field effect transistor and method of manufacturing the same
US9431511B2 (en) Method for producing a semiconductor device comprising a Schottky diode and a high electron mobility transistor
JP5737948B2 (en) Heterojunction field effect transistor, method of manufacturing heterojunction field transistor, and electronic device
US7859014B2 (en) Semiconductor device
EP1405349B1 (en) Algan/gan hemts having a gate contact on a gan based cap segment and methods of fabricating the same
US6797994B1 (en) Double recessed transistor
JP2007324263A (en) Field-effect transistor and manufacturing method thereof
US20070267652A1 (en) Field-effect transistor
US20110233538A1 (en) Compound semiconductor device
US20080251837A1 (en) Semiconductor device and manufacturing method thereof
JP2008153330A (en) Nitride semiconductor high electron mobility transistor
US10998435B2 (en) Enhancement-mode device and method for manufacturing the same
US20120126291A1 (en) Semiconductor device
US8987781B2 (en) Structure of heterojunction field effect transistor and a fabrication method thereof
US7981787B2 (en) Semiconductor device manufacturing method
US6919589B2 (en) HEMT with a graded InGaAlP layer separating ohmic and Schottky contacts
US20220302292A1 (en) Transistor having high withstand voltage and high electron mobility and preparation method therefor
US11699723B1 (en) N-polar III-nitride device structures with a p-type layer
WO2023162521A1 (en) Nitride semiconductor device and manufacturing method therefor
CN114335159A (en) Epitaxial structure of semiconductor device, preparation method of epitaxial structure and semiconductor device
JP2010267817A (en) Field-effect transistor

Legal Events

Date Code Title Description
AS Assignment

Owner name: OKI SEMICONDUCTOR CO., LTD.,JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:IZUMI, TAKAYUKI;SHIGEMASA, RYOJI;OHSHIMA, TOMOYUKI;REEL/FRAME:023138/0705

Effective date: 20090727

Owner name: OKI SEMICONDUCTOR CO., LTD., JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:IZUMI, TAKAYUKI;SHIGEMASA, RYOJI;OHSHIMA, TOMOYUKI;REEL/FRAME:023138/0705

Effective date: 20090727

STCF Information on status: patent grant

Free format text: PATENTED CASE

AS Assignment

Owner name: NEOPHOTONICS SEMICONDUCTOR GK, JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LAPIS SEMICONDUCTOR CO., LTD.;REEL/FRAME:031040/0194

Effective date: 20130329

AS Assignment

Owner name: LAPIS SEMICONDUCTOR CO., LTD., JAPAN

Free format text: CHANGE OF NAME;ASSIGNOR:OKI SEMICONDUCTOR CO., LTD.;REEL/FRAME:031627/0671

Effective date: 20110823

FPAY Fee payment

Year of fee payment: 4

MAFP Maintenance fee payment

Free format text: PAYMENT OF MAINTENANCE FEE, 8TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1552); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

Year of fee payment: 8

FEPP Fee payment procedure

Free format text: MAINTENANCE FEE REMINDER MAILED (ORIGINAL EVENT CODE: REM.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

AS Assignment

Owner name: NEOPHOTONICS CORPORATION, CALIFORNIA

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:NEOPHOTONICS SEMICONDUCTOR GK;REEL/FRAME:063148/0468

Effective date: 20160701

LAPS Lapse for failure to pay maintenance fees

Free format text: PATENT EXPIRED FOR FAILURE TO PAY MAINTENANCE FEES (ORIGINAL EVENT CODE: EXP.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362

FP Lapsed due to failure to pay maintenance fee

Effective date: 20230719